B1742

Step 1: Perform visual inspection of the master mirror control switch assembly for physical damage, broken buttons, or signs of liquid intrusion. Test switch operation manually while monitoring live data for switch input signal changes.

Step 2: Using a digital multimeter, backprobe the mirror switch connector and verify continuity and proper resistance values (typically 0-5 ohms when pressed) on the vertical adjustment circuit while activating the switch up and down.

Step 3: Inspect all connectors in the passenger door harness and at the BCM for corrosion, bent pins, or loose connections. Clean contacts with electrical contact cleaner and apply dielectric grease. Check for proper terminal tension.

Step 4: Test for continuity through the entire circuit from the mirror switch connector to the BCM connector with the harness disconnected at both ends. Look for open circuits, checking particularly at door hinge flex points where wire breakage commonly occurs.

Step 5: If wiring and connections test good, substitute a known-good mirror control switch assembly to verify switch failure. If problem persists with known-good switch and verified wiring, BCM input circuit failure is indicated and BCM replacement may be necessary.

Step 6: After repair, clear codes, cycle the mirror adjustment through full range of motion in all directions, and verify no codes return and proper mirror operation is restored.